diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
index 42ea74635b..c28bb07f44 100644
--- a/libavformat/dashdec.c
+++ b/libavformat/dashdec.c
@@ -1146,6 +1146,7 @@ static int parse_manifest_adaptationset(AVFormatContext *s, const char *url,
 
 err:
     xmlFree(c->adaptionset_lang);
+    c->adaptionset_lang = NULL;
     return ret;
 }